android - Flutter 显示 SnackBar 并在 StreamBuilder 中返回空容器抛出错误

Question

你好，如果现在网络响应返回错误，我正在尝试显示 Snackbar 我的构建函数如下所示:

  @override
  Widget build(BuildContext context) {
    NewsBloc bloc = NewsBloc();
    return Scaffold(
      key: scaffoldKey,
      body: Container(
        color: Colors.white,
        child: StreamBuilder<List<BaseModel>>(
          stream: bloc.newsStream,
          builder: (BuildContext context, AsyncSnapshot<List<BaseModel>> snap) {
            if (snap.hasError) {
              scaffoldKey.currentState.showSnackBar(SnackBar(
                content: Container(
                  height: 100,
                ),
              ));
              return Center(child: Text(snap.error));
            } else if (!snap.hasData) {
              return Center(child: CircularProgressIndicator());
            } else {
              return _newsList(snap.data);
            }
          },
        ),
      ),
    );
  }

它显示了 Snackbar 但也抛出了一个错误:

This Scaffold widget cannot be marked as needing to build
because the framework is already in the procces

Answer 1

那是因为当您的 Widget 正在重建过程中时，您不应该显示 Snackbar，您可以使用的解决方法是:

          _displaySnackBar(BuildContext context) async {
            await Future.delayed(Duration(milliseconds: 400));
            scaffoldKey.currentState.showSnackBar(SnackBar(
              content: Container(
                height: 100,
              ),
            ));
          }

和

   if (snap.hasError) {
          _displaySnackBar(context);
          return Center(child: Text(snap.error));
        }